Third and fourth degree tears (OASI)

Repair of third and fourth degree tears, care of your stitches, and what to expect when healing

For some women the tear may be deeper and extend to the muscle that controls the anus (the anal sphincter).

Third or fourth degree tears, also known as an obstetric anal sphincter injury (OASI), can occur in 6 out of 100 births (6%) for first time mothers and less than 2 in 100 births (2%) of births for women who have had a baby before.